Dropsy is a condition that can have several causes (bacterial/viral). It is seldom contagious but could tell something about waterquality. So desinfection is no use, but looking at filtrage, waterchangeschedule, possible overfeeding, etc.... is useful.
If it was caused by an infection, it's usually Aeromonas which lives in pretty much all freshwater. Even if you were able to eliminate it from the tank it would just be reintroduced with any new fish. One study found that aquarium bacteria was aerosolized by air stones so simply going to an LFS may be enough even if you didn't buy anything.
Improved prevention, diagnosis, and treatment are the solution. High organic loads make diseases more likely. Aeromonas is tricky to treat though and needs different antibiotics some of which are only available from vets.